Nonfunctional ingestion of plant miRNAs in silkworm revealed by digital droplet PCR and transcriptome analysis

Area of Science:

• Molecular Biology
• Entomology
• Plant-Insect Interactions

Background:

• MicroRNA (miRNA)-mediated cross-kingdom communication is a compelling but controversial topic.
• Previous research reported plant miRNA (miR168) cross-regulation of mammalian transcripts.
• The silkworm-mulberry interaction serves as a model for insect-host plant studies.

Purpose of the Study:

• To investigate whether miRNA-mediated cross-kingdom communication is a common phenomenon.
• To determine if mulberry-derived miRNAs transfer to silkworms and affect their physiology.

Main Methods:

• TA cloning, Sanger sequencing, and droplet digital PCR were used to detect mulberry miRNAs in silkworms.
• Synthetic miR166b was administered to assess its uptake and physiological impact.
• RNA sequencing (RNA-seq), RT-PCR, and phenotypic investigations were employed to evaluate physiological changes.

Main Results:

• Several mulberry-derived miRNAs were detected in silkworm hemolymph and various tissues.
• Synthetic miR166b was also found in silkworm hemolymph and fat body.
• Ingested synthetic miR166b did not induce demonstrable physiological changes in silkworms.

Conclusions:

• Mulberry miRNAs are orally transferred to silkworms.
• Despite transfer, no associated physiological processes were demonstrated in the silkworm.
• This study provides a new perspective on the extent and impact of cross-kingdom miRNA transfer.